[petsc-users] Use of PCFieldSplitSetSchurPre

[Jed Brown]

Mark Adams <mfadams at lbl.gov> writes:

> I am creating an Schur complement matrix explicitly (solver%schur) and
> setting it with code like:
>
> call SNESGetKSP(solver%snes,innerksp,ierr)
> call KSPGetPC(innerksp,spc,ierr)
> call
> PCFieldSplitSetSchurPre(spc,PC_FIELDSPLIT_SCHUR_PRE_USER,solver%schur,ierr)
>
> I would think that the "inner" solver would not be used but it is getting
> used.

[...]

> PC Object:(fsa_) 4 MPI processes
>   type: fieldsplit
>     FieldSplit with Schur preconditioner, factorization FULL
>     Preconditioner for the Schur complement formed from A11

I would set a breakpoint at PCFieldSplitSetSchurPre_FieldSplit and then
watch -l jac->schurpre since it appears that your information is being
lost somewhere.
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